The present invention relates to a tomographic imaging system and method.
Intraoperative visualization of target lesions and overlying tissues can reduce the time and invasiveness of surgical procedures, which results in cost savings and reductions in surgical complications. Currently available gamma-ray surgical guidance tools include gamma-ray sensitive nonimaging xe2x80x9cprobesxe2x80x9d. These non-imaging gamma-ray probes resemble classic Geiger counters in appearance. Most modern nonimaging gamma-ray probes have enhanced directional responses (unlike Geiger counters) so that the surgeon can point to structures of interest, and feature a user interface that generates squawks and whistles instead of clicks. Gamma-ray probes are utilized in surgical procedures in which patients are administered radioactive substances prior to surgery. The radioactive substances can be injected systemically, as in the case of tumor-seeking radiotracers (e.g., carcinoembryonic antigen (CEA) analogues for ovarian cancer surgery). In the case of systemic injection, the surgeon""s goal is to detect occult nests of cancer cells for removal to increase the chances for complete tumor kill during chemotherapy. The radioactive substances can also be injected locally, in order to delineate lymphatic drainage patterns (i.e., sentinel node procedure).
Gamma-ray surgical guidance has been attempted for several tumor types. For example, neuroendocrine tumors have been detected intraoperatively with nonimaging probes, even when the tumors were initially missed on magnetic resonance images (xe2x80x9cMRIxe2x80x9d) and computer tomography (xe2x80x9cCTxe2x80x9d) scans. Colon cancer deposits also have been detected with intraoperative nonimaging probes.
Once cancer has been identified, lymphatic drainage patterns can be studied to stage the patient""s disease. For this application, the radioactive substances are injected locally near the site of a known primary cancer, so that the drainage patterns to local lymph nodes can be ascertained. According to the xe2x80x9csentinel nodexe2x80x9d theory, a single node stands at the entryway to more distant sites. Subscribers to this theory attempt to identify and remove this sentinel node. By examining whether the sentinel node contains tumor cells, pathologists aim to predict whether the tumor is likely to have spread to distant locations. Sampling of the sentinel node is preferable to the traditional surgical practice of removing entire blocks of nodes, because of the reduced levels of complications following node removal.
Gamma-ray probes have become the standard of care for surgical procedures involving melanoma in the extremities (i.e., legs and hands). However, for some surgical sites involving complex anatomic regions (i.e., head and neck, axilla, abdomen) the lack of depth and size information provided by simple nonimaging probes can reduce the efficacy of surgical guidance with gamma-ray probes. For example, lymphatic drainage patterns can in some areas of the body be quite complex, and often vary widely from patient to patient.
Some investigators have used small gamma cameras instead of nonimaging probe detector heads. This approach works well for a limited number of scenarios in which, for example, the location of a primary lesion is already specified but the margins are not clear, as in osteoid osteoma.
Unlike primary cancer imaging, in cases where metastatic disease is suspected the surgeon generally does not know a priori where the lesions are located. Because of this uncertainty, what may be an acceptable field-of-view for one patient""s procedure may not be acceptable for the next patient. As a result, no standard camera size can be specified for all surgeries. Because camera field-of-view is related to the overall physical size of the camera, a large field-of-view camera may be too heavy for surgeons to manipulate, or may hinder access to lesions of interest in the close confines often encountered in surgery. Conversely, a small field-of-view camera, while more maneuverable, may not provide information as to the entire extent and location of the lesion.
Additionally, when the camera is moved from one area of interest to another, or from one angular position to another, information from the earliest position is generally not integrated with information from subsequent positions. Also, information concerning the angulation of the camera with respect to the area of interest generally is not recorded. As a result, it is difficult to ascertain the depth of a lesion located in a particular area of interest. In such cases, the camera also does not provide sufficient information to perform a tomographic backprojection or reconstruction, or to obtain a three dimensional image of the lesion.
In one embodiment, the present invention contemplates a tomographic imaging system comprising a moveable detector that is capable of detecting gamma radiation; a position sensor for determining the position and angulation of the detector in relation to a gamma ray emitting source; and a computational device for integrating the position and angulation of the detector with information as to the energy and distribution of gamma rays detected by the detector and deriving a three dimensional representation of the source based on the integration.
The present invention also contemplates a tomographic imaging system comprising a moveable detector that is capable of detecting radiation; a position sensor for determining the position and angulation of the detector in relation to a radiation emitting source; and a computational device for integrating the position and angulation of the detector with information as to the energy and distribution of radiation detected by the detector and deriving a three dimensional representation of the source based on the integration.
The present invention also contemplates a tomographic imaging system comprising a moveable means for detecting radiation; a means for determining the position and angulation of the detector means in relation to a radiation emitting source; and a means for integrating the position and angulation of the detector means with information as to the energy and distribution of radiation detected by the detector means and deriving a three dimensional representation of the source based on the integration.
The present invention also contemplates a method of imaging a radiation emitting lesion located in a volume of interest comprising the steps of positioning a detector that is sensitive to radiation at multiple locations in relation to the lesion to obtain information as to the energy and distribution of the radiation detected by the detector; recording the positions and angulations of the detector in relation to the lesion; integrating the positions and angulations of the detector with the energy and distribution information; and deriving a three dimensional representation of the lesion based on the integration.
The present invention also contemplates a method of imaging a gamma ray emitting lesion in a patient comprising the steps of positioning a gamma camera that is sensitive to gamma radiation at multiple locations in relation to the lesion to obtain information as to the energy and distribution of gamma rays detected by the detector; recording the positions and angulations of the camera in relation to the lesion; integrating the positions and angulations of the camera with the energy and distribution information; and deriving a three dimensional representation of the lesion based on the integration.
The present invention also contemplates a method of radioactive waste surveillance comprising the steps of positioning a detector at multiple locations in relation to the waste, the detector being sensitive to radiation emitted by the waste and providing information as to the energy and distribution of the radiation detected by the detector; recording the positions and angulations of the detector in relation to the waste; integrating the positions and angulations of the detector with the source and distribution information; and deriving a three dimensional representation of the waste based on the integration.